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Effects of laser surface texturing on tribological properties of Ti-6Al-4V in hydroxyethyl-cellulose water-based lubrication
摘要： Purpose – This paper aims to investigate the effect of laser surface texturing on the tribological performance of Ti-6Al-4V disks sliding against Si3N4 balls under hydroxyethyl-cellulose water-based lubrication. The friction coefficients and wear losses of textured and untextured disks were measured and compared. The results indicate that the texture patterns can lead to reduction of friction and wear in the condition of water-based lubrication. Design/methodology/approach – Solutions of hydroxyethyl cellulose were used as water-based lubricants. To find the optimal laser texturing parameters for the best performance enhancement, three line-like patterns were fabricated onto the disks and three machining parameters were used for each type of pattern. Tribological tests were conducted in rotation sliding with ball-on-disk contact configuration on UMT-2. Findings – A higher density of texture lines leads to a larger friction and wear reduction. Compared with untextured disks, the friction coefficient is reduced from 0.043 to 0.028 for textured disks. Some unworn parts were detected in the contact region of the balls against textured disks, which were not found on the balls against untextured disks. The worn surfaces indicated that periodic geometry of the contact track was rebuilt during run-in period, which was beneficial for the formation of lubricant films. Originality/value – In this work, laser surface texturing was used to reduce the friction and wear of Ti-6Al-4V specimens in water-based lubrication, which can be used to improve the tribological performance of Ti-6Al-4V components in mechanical equipment.
关键词： Ti-6Al-4V alloy,Hydroxyethyl-cellulose,Friction reduction,Laser surface texturing,Water-based lubrication
更新于2025-09-09 09:28:46
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Perspectives of the Friction Mechanism of Hydrogenated Diamond-Like Carbon Film in Air by Varying Sliding Velocity
摘要： The purpose of the present work is to probe the friction mechanism of hydrogenated diamond-like carbon (H-DLC) ?lm in air by varying sliding velocity (25–1000 mm/s). Friction tests of Al2O3 ball against H-DLC ?lm were conducted with a rotational ball-on-disk tribometer. As the sliding velocity increases, both the friction coef?cient and the surface wear of H-DLC ?lm decrease, reach the minimum values, and then increase in the high sliding velocity region. Based on the observed results, three main friction mechanisms of H-DLC ?lm—namely graphitization mechanism, transfer layer mechanism, and passivation mechanism—are discussed. Raman analysis indicates that the graphitization of worn surface on the H-DLC ?lm has a negligible contribution to the variation of the friction coef?cient and the surface wear. The origin of the sliding velocity dependence is due to the synergistic interaction between the graphitized transfer layer formation and the surface passivation. The present study will not only enrich the understanding of friction mechanism of H-DLC ?lms in air, but will also help to promote their practical engineering applications.
关键词： transfer layer,sliding velocity,surface passivation,diamond-like carbon ?lm,friction mechanism
更新于2025-09-09 09:28:46
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A Performance Evaluation of a Solar Air Heater Using Different Shaped Ribs Mounted on the Absorber Plate—A Review
摘要： In this paper, the effect of various shapes of ribs used in Solar Air Heaters (SAHs) was discussed. The review is concentrated on the geometry of the rib and its location on the SAH panel. Both numerical and experimental works were considered for discussion with dry air and Nano ?uids as a working ?uid. The in?uence of various shapes, such as an L shape, W shape, V shape, Multiple V shape, V shape with a gap, detachable & attachable ribs etc., was analyzed. The common fact observed from this analysis is that the implementation of arti?cial roughness in the absorber plate results in a considerable increase in the rate of heat transfer. Further, it is observed that ‘Multiple V-shaped with open between the ribs’ results in the maximum thermal enhancement when compared to the other shapes.
关键词： shape of rib,solar air heater,friction factor,heat transfer
更新于2025-09-04 15:30:14
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Universality of strain-induced anisotropic friction domains on 2D materials
摘要： Van der Waals two-dimensional (2D) materials have shown various physical characteristics depending on their growth methods and conditions. Among those characteristics, the surface structural properties are crucial for the application of 2D materials, as the surface structures readily affect their atomic arrangements and/or interaction with substrates due to their atomic-scale thicknesses. Here, we report on the anisotropic friction domains of MoS2 grown not only by chemical vapor deposition (CVD) under various sulfur pressure conditions but also by a mechanical exfoliation process. The 180° periodicity of each domain and the 60° shift between adjacent domains indicate the presence of linearly aligned structures along the armchair direction of MoS2, which is determined by the optical second-harmonic generation method. The anisotropic friction domains of CVD-grown MoS2 ?akes may be attributed to linearly aligned ripples caused by an inhomogeneous strain ?eld distribution, which is due, in turn, to randomly formed nucleation sites on the substrate. The universality of the anisotropic frictional behaviors of 2D materials, including graphene, hBN, and WS2 with honeycomb lattice stacking, which differ from ReSe2 with a distorted triclinic 1T’ structure, supports our assumption based on the linearly aligned ripples along the crystallographic axes, which result from an inhomogeneous strain ?eld.
关键词： strain-induced ripples,chemical vapor deposition,mechanical exfoliation,anisotropic friction domains,Van der Waals two-dimensional materials
更新于2025-09-04 15:30:14
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Quantum electrodynamic cascade structure in a standing linearly polarised wave
摘要： We have performed an analysis of plasma structures formed as a result of the quantum electrodynamic (QED) cascade development in the field of a standing linearly polarised plane wave at various field amplitudes. In view of the spatially inhomogeneous cascade dynamics and complicated particle motion, it is proposed to use spatial distributions of plasma density averaged over the half-period of the field, i.e. integral structures. Based on the analysis of particle trajectories and integral structures with and without allowance for the QED cascade, various plasma structures are revealed and the amplitude thresholds of their occurrence are determined. It is shown that the integral structure maxima may arise not only at the electric field nodes or antinodes, as in a circularly polarised field, but also in the intermediate regions between them.
关键词： electron – positron plasma,quantum electrodynamic cascade,radiation friction
更新于2025-09-04 15:30:14
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Desired Compensation Adaptive Robust Control of Electrical-optical Gyro-stabilized Platform with Continuous Friction Compensation Using Modified LuGre Model
摘要： Continuous friction compensation along with other modeling uncertainties is concerned in this paper, to result in a continuous control input, which is more suitable for controller implementation. To accomplish this control task, a novel continuously differentiable nonlinear friction model is synthesized by modifying the traditional piecewise continuous LuGre model, then a desired compensation version of the adaptive robust controller is proposed for precise tracking control of electrical-optical gyro-stabilized platform systems. As a result, the adaptive compensation and the regressor in the proposed controller will depend on the desired trajectory and on-line parameter estimates only. Hence, the effect of measurement noise can be reduced and then high control performance can be expected. Furthermore, the proposed controller theoretically guarantees an asymptotic output tracking performance even in the presence of modeling uncertainties. Extensively comparative experimental results are obtained to verify the effectiveness of the proposed control strategy.
关键词： three-axis electrical-optical gyro-stabilized platform (TEOGSP),desired compensation friction compensation,Adaptive robust control
更新于2025-09-04 15:30:14
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Tuning the electronic structure of hexagonal boron nitride by carbon atom modification: a feasible strategy to reduce sliding friction
摘要： Essentially, the interlayer interaction of the two-dimensional (2D) layered material is dominant, so it is expected to modify the electronic configuration of the system to change the interlayer interaction for the purpose of reducing interlayer sliding friction. In this paper, using density functional theory (DFT) calculation, we report an effective method to reduce the sliding friction between the two-layer hexagonal boron nitride layers for changing the hexagonal boron nitride electronic structure via introducing carbon. Research results indicate that the increase of the potential energy fluctuation along the sliding path increases with the increase of the load, which is caused by the difference of the degree of interlayer interaction on the sliding path with the increase of the load; at the same time, we found that the appearance of C at the B or N position can promote the interlayer charge transfer to different extents (B position is better than N position) in the BN/BN bilayer, and then produce the effect of reducing the energy barrier on the sliding path between the layers.
关键词： hexagonal boron nitride,charge transfer,friction,electronic configuration,2D material
更新于2025-09-04 15:30:14